I would suggest meeting as many people as possible. I would suggest that you start small with local venues and theatres. You can usually try to volunteer or work the entry
level jobs and meet the local crews and union guys and go from there. If you are talking about music/concerts, try to get into the smaller venues and meet people. Usually, those guys that work there everyday also work the larger venues.
Also, if you are in school, use that. When I lived in NY and went to High School and College there, we were able to go backstage at some great venues. They gave us backstage tours at a few dozen houses in NYC, as well as Boston and Providence. I watched Miss Saigon from backstage and CATS from the
orchestra pit.
I worked union - local crew
stagehand - when I was in college and learned more doing those shows than I did in the technical
theatre classes that I took. It was the mid 90's and as a college student, I got to work everything from Garth Brooks to Jewel to GooGoo Dolls, and more (ok...they were good bands at the time). The best part, they paid very well. Anyone that has worked these type of gigs will tell you, work hard, ask questions, and don't try to impress them with your resume or experience. If they like you, they will probably let you lend a
hand during the show or at least watch. I got hooked up with the job because I went into a live music club in Albany, NY and offered to work for free in exchange for an "apprenticeship". I went in 2-4 nights a week, and helped
load in bands at first, then wired the
stage for each show (mic's, DI's,
etc...), then
monitor engineer, and then
FOH engineer. The guys there asked me if I wanted to make some extra money, and I went to work pushing boxes for concerts.